JPS60143422A - Method and device for recording tracking servo signal - Google Patents

Abstract

PURPOSE:To easily realize highly accurte tracking servo, by using a magnetic head having a spacing gradient to a recording medium in the direction of width of a track and recording a track whose intensity of magnetization is changed in the direction of width with a gradient. CONSTITUTION:A magnetic head 1 is composed of a core section 1A made of a magnetic substance and a spacer section 1B made of non-magnetic substance. The spacer section 1B is used for forming a spacing 1C between the core section 1A and the surface of a magnetic tape 2 and the intensity of magnetization of signals recorded on the track of the tape 2 changes with a gradient in the direction of width as shown in the figure and becomes about a half of the maximum magnetization M at the left end of the width at the center of the width. At the time of tracking servo, a reproducing head 3 composed of a core section 3A whose section that contacts with the surface of the tape 2 is made as a narrow detecting head section 3a and a spacer section 3B that is provided so as to put the detecting head section 3a in it, is used. The reproducing head 3 is suitable for detecting the intensity of a part of magnetization having a gradient in the direction of width of a track 2A and, therefore, highly accurate tracking servo is made more easier.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a method and apparatus for recording tracking servo signals during playback on a magnetic recording medium, and in particular to a tracking servo suitable for tracking servo using the Kerr effect. The present invention relates to a signal recording method and apparatus.

(Background Art) When reading information recorded on a magnetic recording medium, it is necessary to scan the playback head along the recorded trunk. Therefore, when feeding the magnetic recording medium to a fixed playback head, the playback head It is known to servo control the feeding of the medium or the position of the head so that the head does not go off track. This servo control is called tracking servo, but it is technically difficult to perform this tracking servo with high accuracy, and a simple and highly accurate tracking servo method is desired.

(Object of the Invention) In order to meet such demands, the present invention provides a tracking servo signal recording method and an apparatus therefor, in order to realize a method that can perform extremely high-precision tracking servo with an extremely simple structure. The purpose is to provide

(Structure of the Invention) A tracking servo signal recording method according to the present invention records on a tracking servo trunk using a magnetic head having a spacing gradient with respect to the recording medium in the track width direction, thereby increasing the magnetization strength. It is characterized by recording tracks whose width changes with a gradient in the width direction. If a tracking servo trunk is recorded in which the strength of magnetization is continuously changed in the width direction of the track, the recording level can be determined by scanning the center of this track with an extremely small playback head. detect,
By performing servo control to maintain the detection level at a predetermined value, highly accurate tracking servo can be easily achieved.

In other words, for example, if a playback head with a width of several microns is scanned at the center (this does not necessarily have to be the center) of a track with a width of several tens of microns and its output level is detected, fluctuations in the output can be detected. Tracking servo can be performed with high precision using this as a servo input.

Here, the spacing gradient with respect to the recording medium refers to the shape of the magnetic body of the magnetic head, and the distance (spacing) between the recording medium and the recording medium side edge of the magnetic body (head core gap) in the track width direction. It means that the rate of change is changing continuously, and the rate of change may be linear or curved.

Since the strength of recorded magnetization is almost inversely proportional to its spacing, it is thought that a linear change is desirable at the edge.
In short, if changes in recorded magnetization in the width direction of the track can be detected continuously during playback, the degree of the gradient and the way the gradient changes (linearity or non-linearity of the change in spacing)
is not a problem.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 1 is a front view showing an example of a magnetic head used in the tracking servo signal recording method of the present invention, Fig. 2 is a longitudinal cross-section thereof, and Fig. 3 shows the magnitude of signal magnetization recorded by the magnetic head. It is a graph shown in the width direction of a track.

The magnetic head 1 consists of a core part IA made of a magnetic material and a spacer part IB made of a non-magnetic material.
B is for forming a spacing IC between the core portion IA and the surface of the magnetic chip 120, and is obtained, for example, by etching the magnetic film for the magnetic pole as shown in FIG. To form a small head, a thin film head is suitable, a cross section of which is shown in FIG. A conductive coil 13 is disposed between the lower magnetic pole 10 and the upper magnetic pole 110 via an insulating layer 12, and a gap 14 between the lower ends of both magnetic poles 10 and 11 is provided.
is opposed to the tape 2 for magnetic recording. The distance between this gap 14 and the surface of the tape 2 is the aforementioned spacing IC, which changes with a gradient in the width direction of the tape 20 (coinciding with the width direction of the track).

Due to the gradient of this spacing IC, the magnitude of the signal magnetization recorded on the track of tape 2 changes with a gradient in the width direction as shown in FIG. tW/2), the maximum magnetization M at the left end of the width is approximately 1
/2 has a size M/2.

A large number of information signal recording/reproducing heads la including such a servo signal recording head 1.

FIG. 4 shows an example of a multi-head recording system in which Ib, IC, and ld are arranged in parallel. The information recording heads 1a to 1d are provided at mutually fixed positions in parallel with the tracking servo signal recording head 1, and the information recording track 2a is parallel to the tracking servo track 28.

2b, 2c, and 2d are recorded.

Track 2 for tracking servo
A tracking servo signal is recorded in which the magnitude of signal magnetization is changed in the width direction as shown in FIG.

At the time of tracking servo, for example, as shown in FIG.
A reproducing head 3 is used, which is composed of a core section 3A made of a magnetic material, and a spacer section 3B provided with the detection head section 3a sandwiched therebetween. Core section 3A of this playback head 3
is imparted with uniaxial magnetic anisotropy, and its axis of easy magnetization is parallel to the recording medium surface as shown by the arrow in FIG. 5A. The width of the detection head section 3a of this reproducing head 3 is set to a small width (for example, several microns) corresponding to a very small part of the width tw of the track 2A, and is set to a small width (for example, several μ) that corresponds to a small part of the width tw of the track 2A, and is set to a small width (for example, several μ) that corresponds to a small part of the width tw of the track 2A. (shown in FIG. 6) is partially detected. It is desirable that this reproducing head be a magnetic flux responsive head such as an M-type head in order to accurately read out the magnitude of signal magnetization on a one-to-one basis. MR in Figure 5B
The case of the head is shown.

Lead wires 3b and '3c for taking out the signal detection current i are connected to both ends of M1 (in the case of a head, M11) and element 3'. The detection head section 3a' is the same as the reproducing head 3 described above.

Another example of a magnetic flux responsive reproducing head is one that utilizes the Kerr effect.

As schematically shown in FIG. 7, a laser beam 5A is projected onto the surface of the core portion 3 of the head 3 shown in FIG. The two tracking servo tracks of the tape 2 detected by the head 3 are detected by detecting the reflectance of the head 30, which changes due to the Kerr effect, depending on the magnetization size of the two tracking servo tracks of the tape 2 detected by the head 3. It detects the magnitude of magnetization at a certain point. This reproducing head 3 has a detection head section 3a shown in FIG. 5, and the magnitude of magnetization in a very small portion of the width of the track 2 is detected by this detection head section 3a. This head uses the Kerr effect, so it can detect a signal that corresponds to the magnitude of magnetization of the medium.
Magnetic flux response type detection can be performed like a head.

Therefore, it is particularly suitable for detecting the magnitude of a portion of magnetization having a gradient in the width direction of two tracks, as in the present invention, and facilitates high-precision tracking servo.

In the tracking servo system, the level of the detection signal obtained as described above is fed back to a means for controlling the relative position of the head and tape so as to maintain it at a constant level, and the well-known servo control method is used. The method can be adopted as is.

As an example, a circuit as shown in FIG. 8 is adopted. In FIG. 8, the reproducing head 3, the laser source 5B,
The photodetector 6 is the same as that in FIG. The output of the photoelectric detector 6 is amplified by an amplifier 7, detected by a diode 8 (assuming that the signal magnetization at this time is recorded as an alternating current), and a DC output corresponding to the amplitude is sent to a differential amplifier 90 on the inverting side. The output of the differential amplifier 9 is input to a well-known servo mechanism 21, and the non-inverting side human power 9b is connected to a voltage source 2 (Ml''-) that supplies a constant voltage. The position of the reproducing head 3 is controlled by the mechanism 21 .

In this way, the reproducing head 3 is subjected to servo control, and its position is controlled in accordance with the level set by the constant voltage source 20. At this time, if the level set by the constant voltage source 20 is adjusted to the magnetization magnitude M/2 at the center of the two tracks, the position of the reproducing head 3 is always servo-controlled to the center of the two tracks.

The configuration of a reproducing thin film head using the Kerr effect is disclosed in a patent application filed on December 29, 1988 by the same applicant (
1) and (2).

Next, other embodiments of the present invention will be described with reference to FIGS. 9 to 12. FIG. 9 shows a head group 3 that includes an erasing head 31, a recording head 32, and a reproducing head 33.
1 is a cross-sectional view showing an example in which recording is performed on a magnetic tape 2 using 0, and further reproduction from the magnetic tape 2 is possible. In the following embodiment, an example will be shown in which two sets of this head group 30 are used for tracking servo.

FIG. 10 shows a track 2A for two tracking servos, using an integrated erase head 31A as two erase heads.

An example of recording 2B side by side is shown. Recording head 32A, 3
2B is symmetrically spaced 3 as shown in Figure 11 (5).
2a and 32b have opposite slopes, which makes the first
Track 2A has a signal magnetization strength with an opposite gradient as shown in Figure 1 (B).

2B can be recorded simultaneously in parallel.

The two tracking servo tracks 2A and 2B, in which the magnitude of signal magnetization is increased in opposite gradients, are processed by the reproducing heads 33A and 33B using the Kerr effect or M
When scanning and detecting using the R effect, outputs 35A and 35B that change inversely depending on the positional deviation of the playback heads 33A and 33B are obtained as shown in FIG. 11 (DJ). These two outputs 35A, 35B is replaced by another amplifier 36A as shown in FIG.

36B, and when input to the adder 38 via opposite diodes 37A and 37B, both outputs 35A.

35B is input to the servo controller 39, and in response to this, feedback is applied such that the positions of the playback heads 33A, 33B are corrected only when there is a difference between the two rivers 35A, 35B. tracking servo is performed.

According to this embodiment, since the outputs of the reproducing heads 33A-33B are doubled and used for control, the S/N of control is improved and more accurate control is possible.

In each of the above embodiments, the recording head 1.32A,
32B spacing IC.

32 a and 32 b both have linear slopes, but they may also have curved slopes (including upward convex, downward convex, and S-shaped slopes).

(Effects of the Invention) According to the method and apparatus of the present invention, a track having a magnetization gradient in the width direction can be easily recorded on a magnetic recording medium as a track for tracking servo.
Tracking servo can be easily performed using a reproducing head having a detection width smaller than the track width.

Furthermore, since a recording head having a spacing gradient in the width direction of the track is used to record this track, the tracking servo track can be recorded very easily.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the end of an example of a magnetic head for recording tracking servo signals used in the present invention, Fig. 2 is a longitudinal cross-sectional view thereof, and Fig. 3 is a signal of a track recorded by the magnetic head. A graph showing the magnitude of magnetization in the width direction of the track, Figure 4 is a perspective view showing an example of a multi-head, and Figure 5A is a graph showing an example of a multi-head used when performing tracking servo by reproducing tracks recorded by the present invention. FIG. 5B is a front view showing an example of reproduction by an MR head that utilizes the MR effect. FIG. 6 is a tracking servo reproduced by the reproduction head of FIG. 5A. A graph showing the signal output. Figure 7 is a perspective view showing the reproduction using the Kerr effect using the reproduction head of Figure 5A. Figure 8 shows the tracking servo being controlled by the reproduction signal. FIG. 9 is a side sectional view showing the other side of the head used in the method of the present invention; FIG. 10 is a plan view showing another embodiment of the present invention. Figures 11 (A), (B), (C), and (D) respectively show a recording head (5), a recording signal (B), a playback head (C), and a playback signal (D) in this embodiment. FIG. 12 is a circuit diagram showing a tracking servo circuit used in this embodiment. 1, 32A, 32B... Track recording head IA... Magnetic core portion IB... Spacing 2.
...Magnetic tape 2A, 2B...Track 3 for tracking servo,
33A, 33B, ... Reproduction head 1i 5A
Figure “〃 “, 7. ff 33A 33B 35B Fig. 12

Claims (1)

[Claims] 1) A method for recording a tracking servo track extending in the feeding direction of the medium on a magnetic recording medium, in which the spacing of the magnetic recording medium has a gradient in the width direction of the track. A tracking servo signal recording method, comprising recording the tracking servo track using a magnetic recording head. 2) A tracking servo signal recording device comprising a magnetic recording head whose spacing with respect to a magnetic recording medium is inclined in the width direction of a track for recording tracking servo. 3) Asahi 1's magnetic recording head in which the spacing for the magnetic recording medium is sloped in one direction in the width direction of the recorded tracking servo track, and a magnetic recording head in which the spacing is sloped in the opposite direction to the one direction. 1. A tracking servo signal recording device comprising: 2 magnetic recording heads.